Air conditioning control system



, Jan. 26, 1943. L. B. MILLER ETAL 1 AIR CONDITIONING CONTROL SYSTEM Filed Aug. 23,- 1935 s Shgets-Sheet i new uvm wan ZI P .Le'o B.Mil ler Henry E'Dever non ' Jan. 26, 1943. B. MILLER ET AL AIR CONDITIONING CONTROL SYSTEM Filed Aug. 25; 1955 s Sheets-Sheet z Leo B. Miller Henr mu m B.

yEDever Jan. 26, 1943.

L. B. MILLER ETAL AIR CONDITIONING CONTROL SYSTEM Filed Aug. 23, 1935 a Sheets-Sheet 3 DEHUMIDIFYING COIL RETURN AIR Lea B. Miller Henry I? .Dever excessive undesirable value.

Patented Jan. 26, 1943 UNITED STATES PATENT OFFICE 2,309,411

AIR. CONDITIONING coNrRor. SYSTEM Leo B. Miller, Bronxville, N. Y., and Henry F.

Dever, Minneapolis, Minn., assignors to Minneapolis-Honeyweli Regulator Company, Minneapolis, Minn., a corporation of Delaware V Application August '23, 1935, Serial No. 37,606 35 Claims. (01. 257-3) The present invention relates to an improved control system for conditioning the air in a space during all types of weather.

One of the objects is the provision of an improved control system for controlling the cooling, dehumidification, heating, humidifying, supplying of fresh air, and all other phases of a complete all-year air conditioning system.

More specifically, an object of the present invention is the provision of an improved control system for conditioning air in the summer by which the air in a space is maintained at a substantially constant effective temperature. In addition, it is a further object of the invention to vary the effective temperature of the air in the space upon fluctuations in a condition of the outdoor atmosphere and in such manner that the effective temperature in the space is increased as the outdoor temperature rises above some predetermined value. Any desired type of diflerential may be maintained between the indoor effective temperature and the outdoor condition, which may be outdoor dry bulb temperature, but preferably the arrangement is such that a variable differential is maintained between these conditions.

Another object of the invention is the provision of a summer air conditioning system wherein theefi'ectiv'e temperature in the space is maintained substantially constant or is varied within a predetermined range upon variations in an outdoor condition, the arrangement being such that this substantially constant effective temperature or the effective temperature range maintained upon variations in the outdoor conditions is obtained by allowing the relativehumidity in the space to .obtain the desired efiective. temperature and super-imposing upon this control a limiting means to prevent the relative humidity from rising to an A further object of the invention is the adding of heat to the air in the space in the event the removal of moisture therefrom by a cooling process when the relative humidity becomes excessive causes the temperature of the air to become too low. This control is preferably by the temperature of the air being discharged into'the space rather than by the temperature of the air in the 'of a heating system wherein the effective teme perature of a space is maintained substantially constant by controlling the humidity and dry bulb temperature thereof to maintain desired values or ranges of relative humidity and dry bulb temperature, the value or range .of the relative humidity maintained being lowered as the outdoor temperature lowers. whereby to prevent condensation or moisture upon windows and other exposed surfaces and at the hame time raising the value or range of the dry bulb temperature main-, tained in the space to compensate for such lowering in the relative humidity whereby the effective temperature is maintained substantially constant.

Another object of the invention is the provision of an improved heating system for a space wherein control means operate normally to maintain the space temperature above a predetermined minimum, together with means to increase the I mer cycle. Specifically, when the apparatus is. operating on a winter cycle, the supply of fresh air is increased if the space temperature becomes excessive whereas the supply of fresh air is decreased upon either a rise or fall 'of an outdoor condition above and below an optimum value when the apparatus is operating on a summer cycle.

Another object of the invention is the provision of a novel heating control wherein a heating means is controlled tomaintain a substantially constant temperature during the. winter and is additionally controlled in the summer to prevent too low a temperature as a result of removal of space after. the conditioned -air has diffused therein.

Another object of the invention is the provision of summer air conditioning systems of the class moisture from. the space by a temperature lowering process.

A' further object of the invention is the provision of an improved automatic control for changing the system from winter operation to summer operation wherein this change is effected through the combined action of means responsive to a condition in the space and a condition of the .outside atmosphere. More specifically, the apparatus is maintained on a summer cycle if either the space temperature is above a predetermined value or within a predetermined relatively narrow and the other of which is controlled by an outdoor temperature responsive thermostat, having a relatively wide differential of operation.

Further objects of the invention include all of the phases of operation of the winter system, all the phases of operation of the summer system, the operation of the complete system, both summerand winter, and combinations of various specific phases of controlherelnbefore set forth and which will be found in the drawings, the detailed description, and the appended claims.

For a more complete understanding of the invention, reference may be" had to the following description and accompanying drawings, in which:

Fig. 1 is a diagrammatic showing of the general layout of the system together with a specific showing of the summer-winter change-over mechanism as well as thsnmmer cooling and dehumidifying control;

Fig. is a detailed showing of the manner in which the fresh air'damper is controlled, both in the summer and the winter, and

' Fig. 3 is a detailed showing of the winter heat- .ing control as well as the dehumidifying control.

Referring to Fig-1 of the drawings, an airconditioning unit or an apparatus is herein diagrammatically shown as comprising an air conditioning chamber l8 in the form of a duct which communicates with a fresh air inlet duct II and a return air duct l2. The amount of fresh air taken in through the fresh air inlet duct ll and delivered to the air conditioning chamber i8 is controlled by a damper l3 which is located in the fresh air inlet duct l I and is pivoted upon a shaft M. This shaft I4 is controlled by a motor mechanism l8 which drives a crank l8. This crank I8 is connected to a similar crank ll that is secured to shaft l4. The cranks l8 and I! are connected by a link it. The manner in which the motor mechanism l8 controls the fresh air damper l3, both in the summer and the winter, will be explainedin detail hereinafter.

Located within the air conditioning chamber 88 is a dehumidifying coil is, a cooling coil 28, a heating coil 2 I, and a water spray 22. The dehumidifying coil l8 and the cooling coil 28 are adapted to besu'pplied with a suitable source of refrigerating medium under the control of proper temperature and humidity responsive controls in a man-v ner to be explained hereinafter, and, similarly, the heating coil 2i is adapted to be supplied with suitable heating medium under the control of Proper temperature controls and the water spray 22 is supplied with water for humidifying the air passing through the air conditioning chamber l8, all as will hereinafter appear.

The summer-winter change-over mechanism The system of the present invention is constructed to condition air for a space both during the winter and during the summer so asto supply air at the proper temperature and humidity in relation to outdoor conditions. It is, of course, desirable to supply mechanism for changing the control system to winter operation or summer operation and vice versa and this mechanism will now be described.

The summer-winter change-over mechanism is entirely electrical and includes a relay generally indicated at 25. This relay 28 includes a relay coil 28 and a cooperating armature 21 which controls a plurality of switches. Specifically, the armature 21 controls switch arms 28, 28, 38, 3| and 32. The switch arm 28 cooperates with a pair of contacts 33 and 34, the arrangement being such that switch arm 28 engages contact 33 when the relay coil 28 is deenergized and engages contact 34 when the relay coil 28 is energized. The switch arm 28 cooperates with a single contact 38 and engages the same when the relay coil 28 is energized. The switch arm 38 cooperates with two contacts 38 and 31, and the arrangement is such that switch arm 38 engages contact 38 when relay coil 28 is deenergized and engages contact 31 when this relay coil is energized. Switch arms 3| and 32 both cooperate with pairs of contacts, switch arm 3| cooperating with contacts 38 and 38 whereas switch arm 32 cooperates with contacts 48 and 4|. The arrangement is such that switch arm 3| engages contact 38 and switch arm 32 engages contact 48 when relay coil 28 is deenergized. On the other hand, switch arm 3| engages contact 33 and switch arm 32 engages contact 4! when the relay coil 28 is energized. Energization of relay coil 28 is controlled by a pair of thermostats, one of which is designated at 42 and responds to outdoor temperatures, and the other of which is designated at 43 and responds to the temperature of the space being controlled.

The outdoor thermostat 42 comprises a pressure responsive actuator in the form of a bellows 44 which is connected to a controlling bulb 48 by means of an interconnecting tube 48. The bellows, bulb and tube are all charged with a suitable amount of expansible fluid as is wellknown in the art. The controlling bulb 48 may be located in any desired position so as to respond to 'outdoor temperature and is herein shown as conveniently located in the fresh-air inlet duct 1 i. The bellows 44 operates a switch carrier 41 which is pivoted at 48 and supports a mercury switch 49. This thermostatic switching mechanism is so arranged that mercury switch 49 is moved to circuit closed position when the outdoor temperature rises to 75 1. and remains in circuit closed position until the outdoor temperature falls to 65 F.

The indoor temperature responsive switching mechanism 43 is similar to-the outdoor temperature responsive switching mechanism 42 and also includes a pressure responsive actuator in the formof a bellows 88. This bellows 88 is connected to a controlling bulb 8! by a suitable connecting tube 82' and the bellows, bulb and connecting tube are charged with a suitable amount of volatile or expansible fluid as is wellknown in the art. The bellows 88 operates a switch support 83 that is pivoted at 84. The switch support 83 carries a'mercury switch 88.

temperature rises to 75 F. or thereabove and moves to open position whenever the indoor temperature falls below 75 F.

The mercury-switches 49 and 55 of the outdoor temperature responsive controller 42 and the indoor temperature responsive controller 43' are connected in parallel for the purpose of energizing and deenergizlng the relay coil 26. Either the mercury switch 49 or the mercury switch 55 can cause energization of the relay coil 26. The circuit for relay coil 26 that is controlled by mercury switch 49 is as follows: line wire 56, wire 51, mercury switch 49, wire 58, wire 59, relay coil 26 and line wire 66. Similarly, the circuit by which relay coil 26 is controlled by the mercury switch 55 is as follows: line wire 56, wire 6|, mercury switch 55, wire 62, wire 66, relay coil 26 and line wire 60.

From the foregoing description, it will be eviany 55 moves to closed position whenever the indoor dent that whenever the outdoor temperature.

rises to 75 F., the mercury switch 49 will be closed and the relay coil 26 will be energized. The relay coil 26 will then remain energized until the outdoor temperature falls to 65 F., so as to open mercury switch 49. The mercury switch 55 exerts a supplemental control in that it causes energization of the relay coil 26 whenever the indoor temperature is at or above 75 F., whereby the relaycoil 26 cannot be deenergized even though the mercury switch 49 be opened. In this manner, placing of the'system on winter operation when the outdoor temperature is below 65 F. or when the outdoor temperature" is below 75 F. when it has formerly been below 65 F. (the mercury switch 49 being open under either condition) is prevented in the event the indoor temperature is "75 F. or thereabove. Under these conditions, it will be obvious that a heating action is not necessary or desirable. With the parts in the position shown, it will be evident that the outdoor temperature has recently been at or above 75 F. since the mercury switch 49 is closed. It will be further evident that the outdoor temperature is not below 65 F. because the mercury switch 49 is closed, but the indoor temperature is below 75 F. since switch 55 is open.

' Under these conditions, the relay coil 26 is energized and the relay has its parts positioned as shown in Fig. 1 so that the system is operating on its summer cycle.

Fresh air damper control Turning now to Fig. 2 of the drawings, the

66 in the opposite direction when its associated field-winding II is operatively energized. It will therefore be seen that the two motors comprised by the rotors 68 and field winding 16 and the rotor 69 and field winding 1| comprise a form of reversible motor means.

Operative energization of the field windings l6 and 'H is controlled by a double-circuit switch= ing mechanism which comprises a movable switch arm 12 that is disposed between a pair of cooperating contacts 13 and 14. The switch arm 12 is positioned by a single magnetic plun er 15 which is connected thereto through a suitable I non-magnetic and non-conducting connection 16. This single plunger 15 is primarily controlled by a pair of normally equally energized coils l1 and 18 which may takethe form of entirely separate coils or may conveniently be arranged by providing a single coil with a centertap. The plunger 15 is additionally controlled by a pair of auxiliary windings l9 and 88, each of which is provided with a relatively small number of turns.

The energizations of solenoid coils Ti and 16 are always maintained substantially equal or the energizations thereof are immediately equalized as will become apparent hereinafter. During the summer, unbalancing of the'energizatlons of the solenoid coils l7 and 16 results from changes in outdoor temperature and is brought about through the agency of an outdoor temperature responsive variable resistance controller or potentiometer thermostat indicated generally at M. a

This potentiometer thermostat 8i includes a resistancecoil 82 and a cooperating contact arm 63 which forms one arm of a bell crank that is pivoted at 84. The other arm 65 of this bell crank is operated by a pressure responsive device herein shown in the form of a bellows 66 This bellows 86 is connected to a controlling bulb 81 by means of a tube 88. The bellows, controlling bulb and tube are charged with a suitable volatile or expansible fluid and the pressure created thereby is opposed by a spring 89 which acts .upon the arm 85 of the bell crank in a well-known manner. The controlling bulb 81 may be located at any desired place so long asit responds to outdoor temperature and is herein shown as conveniently located in the fresh air inlet duct ll.

' The controlling resistance 62, instead of being ing shaft 65 to which the crank I6 is secured,

This main operating shaft 65 is connected-to rotor shaft 66 through suitable reduction gearing, generally indicated at 61. Secured to this rotor shaft 66 are two rotors 68 and 69. A field winding I0 cooperates with the rotor 68 and a similar field winding ll cooperates with the rotor 69. The arrangement is such that rotor 68 rotates rotor shaft 66 in one direction when its associated field winding 16 is operatively energized and the rotor 69 rotates the rotor shaft,

wound uniformly, is wound in a tapered fashion so that the amount of resistance change per unit of movement of the contact arm 83 varies as the contact arm 83 moves from one end of this resistance 62 to the other end thereof. The arrangement is such that contact arm '63 traverses the complete resistance 82 upon a 15 degree change in outdoor temperature, the contact arm 83 engaging the left-hand end of. resistance 62 when the outdoor temperature is 65 F. and engaging the right-hand end thereof when the outdoor temperature is F. The tapered winding of the resistance 82 is of such nature that when the outdoor temperature is 70-F.,

so that the contact arm 83 is in the position shown,-this contact arm 83 engages the electical center of the resistance 82 although it is disposed to the left of the geometric center thereof. As a result, if the temperature falls from 70 F. .to 65 F., the contact 63 will traverse the same amount of effective resistance as if the temperature rises from 70 F. to 80 F. It will be understood, of 'cours,.that these values vJust set forth are only one of many posslblelsets of conditions that may be utilized in controlling the fresh air damper I3.

The controller 8! also includes an auxiliary switch that comprises a. stationary switch arm 90 and a cooperating movable switch arm or contact 9| which is operated by contact arm 83.

In Fig. 2 of the drawings, this is shown as being accomplished by connecting the contact 9| to the contact arm 83 through the medium of a piece of insulation 92. such that the contact 9 I engages the switch arm 90 when'the outdoor temperature has risen to some excessive value such as 85 F. It will therefore be evident that the contact 9| does not engage the switch arm 90'until the outdoor temperature has risen. sufficiently to cause contact arm 83 to completely traverse the resistance 82 and pass beyond the right-hand end thereof.

During the summer, the energizations of the solenoid coils 11 and 18 are also adapted to be controlled to a minor extent by means of a manually operable rheostat 95 which comprises a resistance 96 and cooperating contact arm 91.

During the winter operation, the respective energizations of coils I1 and 18 are adapted to be manually varied by a manual rheostat 98 that includes a resistance 99 and a cooperating contact arm I00. The energizations of these solenoid coils I1 and 18 are additionally adapted to be controlled automatically, under certain abnormal conditions, .by means of a portion of a temperature responsive controller, generally indicated at. --IOIl -"-.'I'his temperature responsive controller I 0 I'*re sponds to the temperature of the space and-includes a pressure responsive actuator in the form'of a bellows I02 that is connected to a controlling bulb I03 by means of a connecting tube I04. The bellows, tube and controlling bulb are suitably charged with vola- The bellows I02 operates an arm I05 which is secured to a shaft I06. A spring I0-I opposes movement of the arm I05 by the bellows I02.

This shaft I06 carries two contact arms I08 and I09. Contact arm I08 cooperates with a resistance IIO that is wound upon a support III. 4 One end of this resistance .0 is connected to a conducting sleeve I I2 which is likewise mounted upon the support III. In a similar manner,'the

'contact arm I09 cooperates with a resistance H3 which is wound upon a support I I4 and is also adapted to slide upon a conducting sleeve II5 which is-mounted upon this same support II4. As before stated, the thermostatic controller IOI responds to the temperature of the space being controlled and the controlling bulb I03 may be located in any suitable portion of said space but is here shown conveniently located in the return air duct I2. With the prevailing temperature at 10 the contact arm I09 is engaging resistance H3 at its right-hand end and the contact arm I08 is engag g sleeve II2. When the temperature rises to 74 F., contact arm I09 is moved to the left-hand end of resistance H3 and contact arm I08 is moved to I the right-hand end of resistance IIO. Iii the temperature continues to rise until it reaches 18 F., the contact arm I08 merely moves along the sleeve II! but the contact arm I08 completely traverses the resistance III and is then positioned at the extreme left-hand end there- 7 The arrangement is 10 and its resistance III cooperates with the manual rheostat 88, under certain abnormal conditions, to control the fresh air damper I3 during the winter operation of the apparatus.

Low voltage electrical power is supplied to the motor mechanism 1 5 and the associated solenoid coils, auxiliary windings and resistances by means of a step-down transformer I20 that is provided with a high voltage primary I2I which is connected to suitable line wires. The step-down transformer I20 is also provided with a low voltage secondary I 22. Whenever the switch arm 12 engages contact 13, the field winding II and the auxiliary winding 19, in series, are energized by a circuit as follows: secondary I22, wire I23, wire I24, switcharm 12, contact 13, wire I25, auxiliary winding 19, wire I26, field winding II, wire I21 and wire I28 to the other side of sec-, ondary I22. Similarly, whenever the switch arm 12 engages contact 14, the field winding 10 and the auxiliary winding 80, in series, are energized by a circuit as follows: secondary I22, wire I23, wire I24, switch arm 12, contact 14, wire I29, auxiliary winding 80, wire I30, field winding 10, wire I21 and wire I28 to the other side of secondary I22. The solenoid coils 11 and 18, in series, are connected across secondary I22 by wires I23, I3I, I32 and I28.

Irrespective of whether the system is operating on a summer or winter cycle and irrespective of what particular automatic or manual controller causes an unbalance in the energizations of solenoid coils 11 and 18, these energizations are rebalanced by a balancing potentiometer, generally indicated at I33, which comprises a balancing resistance I34 and a balancing conof the motor mechanism I5 so as to be positioned tile or expansible fluid, as is usual in the art.

thereby. The upper end of balancing resistance I34 and the left-hand end of control resistance. 82 are interconnected by wires I36 and I31 and are connected to the left-hand end of solenoid winding 11, through a protective resistance I39, by wires I38 and I40. The lower end of balancing resistance I34 is connected to the righthand end of solenoid coil 18, through a protective resistance I, by wires I42 and I43. The contact 35 of the change-over relay 25 is connected to the junction of wires I42 and I 43 by a wire I44. The associated switch arm 29 is connected to the contact arm 91 of rheostat 95 and to the switch arm by wires I45, I46 and I41. One end of resistance 96, the right-hand end of control resistance 82, and the contact 9I are inter-connected by a wire I48.- The junction of solenoid coils 11 and 18 is connected to a manual switch I49 and to the. balancing contacting finger I35 by wires I50, I5I and I52.

The manual switch I49 is' also connected to switch arm 30 of the change-over relay 25 by a wire I53. The cooperating contact 31 is connecited to the control contact arm 83 by a wire 15 i I I With the parts in the positions shown, the contact arm 91 of the manual rheostat 95 is engag ing the extreme left-hand end of resistance 98 so that none of this resistance is connected in the circuit. Also, the control contact 83 is engaging the electrical center of the control resistance 82 and the balancing contact finger I35 is engaging. theelectrical center, as well as the geometrical center, of balancing resistance I34. Equal portions of control resistance 82 and equal 75 portions of balancing resistance I34 are therea,soa,411

fore connected in parallel with the solenoid coils 11 and I3 so that both of the solenoid coils are traversed by the same amount of current. The

magnetic plunger I5 is therefore centrally positioned, asshown, and the switch arm I2 is intermediate contacts I3 and I4 so that neither of.

somewhat, control contact 33 will move along control resistance 82 towards its left-hand end. This reduces the amount of control resistance 32 which is connected in parallel with the solenoid coil 11 so that more current flows through this portion of the control resistance 82 and less flows through the solenoid coil 11, whereupon the energization of solenoid coil I1 is reduced below that of solenoid coil I3. When this diiference in current flows becomes sufliciently great, plunger I5 will move to the right sufficiently far to bring switch arm I2 into engagement with contact I4. When this occurs, field winding I is energized by the circuit described above and the auxiliary winding 30 is likewise energized. This energization of the small auxiliary winding 30 exerts further magnetic force on plunger I tendwire I 31, wire I33, protective resistance I33 and ing to move the same towards the right and thereby increases the pressure between switch arm 'I2 and contact 14. Energization of field winding I0 causes rotation of its associated rotor 63 in such direction that main operating shaft 55 is rotated in a counter-clockwise direction as viewed from the left. As a result, the crank I6 is rotated in a similar direction and the fresh air damper I3 rotates in a counter-clockwise direction towards a vertical position in which less' air is allowed to fiow through the fresh air inlet duct II. This counterclockwise rotation of main operating shaft 65 causes balancing contact finger I to move along balancing resistance I34 toward its lower end. As this balancing contact finger I35 moves along the balancing resistance I34 towards the lower end thereof, less of the balancing resistance I34 is in parallel with the solenoid coil I8 so that the current flow through the solenoid coil I3 is reduced in respect to the flow of current through solenoid coil 11-. When the balancing contact finger I35 has traveled along balancing resistance I34 in this direction sufliciently far to substantially equalize the energizations of solenoid coils TI and I3, plunger I5 moves back toward its central position far enough to move switch arm I2 from engagement with contact I4. The auxiliary winding 80 and the field winding I0 are thereupon deenergized. Deenergization of auxiliary winding 30 removes the additional attracting force tending to move plunger I5 to the right, whereupon plunger 15 moves further to the left so that switch arm I2 is widely spaced from contact I4 as well as from contact I3 thereby insuring a good clean break between switch arm I2- and contact 14. Deenergization of field winding 10 stops the counterclockwise rotative movement of main operative shaft 55. The damper I3 has now been rotated toward its vertical position in a counter-clockwise direction so as to reduce the flow of fresh air through the fresh air duct I I. This new position it being remembered that of damper I3 corresponds to the new position of control contact 33 upon control resistance 32.

If the outdoor temperature should fall to 65 F., control contact 33 will engage the extreme lefthand end of control resistance 82 and solenoid coil 11 will thereupon be substantially short-circuited. Starting with the junction of solenoid, coils I1 and I3, this substantial short-circuit for solenoid coil 11 can be traced by way of wire I50, wire I5I,- manual switch I43, wire I53, switch arm 30, contact 31, wire I54, control contact 83,

wire I40 to the left-hand end of solenoid coil II.

This circuit does not completely short-circuit solenoid coil II by reason of inclusion of the protective resistance I33 therein but the amount of current flowing through solenoid coil II under these conditions is relatively small. However, this current flow is large enough to exert an attractive force upon the plunger I5. Solenoid coil I3 is now again more highly energized than the associated solenoid coil II whereupon plunger I5 will once more move to the right and bring switch arm I2 into engagement with'contact I4. Auxiliary winding 30 and field winding I0 will now be energized, in series, by the circuit described above. The main operating shaft 65 is again rotated in a counter-clockwise direction and will continue to so operate until balancing contact finger I35 engages the extreme lower end of balancingresistance I34. At this time, solenoid coil 73 is also substantially short-circuited by a circuit which is as follows: starting with the junction of solenoid coils II and I8, wire I50, Wire I52, balancing contactfinger I35, wire I42, wire I43, and protective resistance Hi to the righthand end of solenoid coil I8. The energizations of solenoid coils II and I3 are now again substantially equalized whereupon switch arm 12 will move from engagement with contact 14. Auxiliary winding 30 and field winding 10 are of main operating shaft 65 in counter-clockwise f direction which has now taken place, positions fresh air damper I3 in its vertical position so that no fresh air is permitted to fiow through the fresh air duct II.

If the outdoor temperature should rise somewhat, the control contact 33 will move along control resistance 32 towards its right-hand end, it is now at the extreme left-hand end thereof. Part of the control resistance 32 is thereupon placed in parallel with the solenoid coil I1 whereupo more current flows through this solenoid coil than flows through solenoid coil I3. When t 's temperature rise has been sufiicient, the solenoid coil I] will be sufficiently more highly energized than the solenoid coil I3 to cause plunger 15 to move to the left and bring switch arm 12 into engagement with contact I3. When this occurs, the auxiliary winding I9 and the field winding 1 I, in series, are energized by the circuit set forth above. Rotor 69 now drives main operating shaft 65 me. clockwise direction as viewed from the left. Balancmg contact finger I35 therefore begins moving upwardly along balancin resistance I34 and the fresh air damper I3 is the horizontal position This quarter revolution ancing resistance I34, part of this balancing resistance I34 is placed in parallel with solenoid coil 18 so that the current flow through this solenoid coil increases. when the energizations of solenoid coils I1 and I8 have been substantial- 1y rebalanced, plunger 15 will move far enough to the right to disengage switch arm I2 from contact 13. The auxiliary winding I3 and the field winding II are thereupon deenergized. Deenergization of the auxiliary winding I9 removes the additional attractive force upon plunger 15, tending to move the same to the left whereby plunger 15 moves further to the right and widely spaces switch arm 12 from contact I3. 'I'he deenergization of field winding 'II causes main operating shaft 65 to cease its clockwise rotative movement so that further opening movement of fresh air damper I3 ceases. The fresh air damper I3 has now been moved toward the horizontal position which it originally assumed so that some flow of outdoor air is permitted through the outdoor inlet duct I I.

As the outdoor temperature continues to rise, the outdoor inlet damper I3 wiJl continue to move in clockwise direction and when the outdoor temperature has returned to 70 F., the parts will again be in the position shown in Fig. 2 wherein the fresh air damper I3 is in its horizontal position and a full flow of outdoor air'is permitted through the fresh air inlet duct II. If the outdoor temperature should continue to rise, the clockwise rotation of the main operating shaft 85 will continue as will the clockwise movement of fresh air damper I3 which now moves towards its vertical position while moving in clockwise direction and thereby again reduces the flow of fresh air through the fresh air inlet duct II. If the outdoor temperature rises to 80 F., the control contact 83 will engage the extreme right hand end of control resistance 82, whereupon the balancing contact finger I35 must move to the extreme upper end'of balancing resistance before the energizations of solenoid coils I1 and I8 are again substantially balanced. As a result, the fresh air damper I3 will again have been moved to its vertical position by this time by reason of clockwise rotation rather than counterclockwise rotation.

It. is usually desired to maintain a small flow of fresh outdoor air into the air conditioning chamber, and therefore into the space'to be conditioned, during the summer even though the outdoor temperature does become relatively high. If it be desired to do this, manually operable rheostat 95 is operated by moving manual contact arm 91 along the associated resistance 38 towards its right-hand end whereby part of the resistance 96 is placed in circuit with control resistance 82. If this be done, it will be apparent that when the control contact 83 engages the extreme right-hand end of control resistance 82,

part of the resistance 38 will still be in parallel with the solenoid coil I8. Under these conditions, the current flow through' solenoid coil 18 will not be reduced as much as if this portion of resistance 98 were not included in circuit therewith. As a result, balancing contact finger I38 will move to a position in which the energization of the solenoid coils l1 and I8 are substantiallyrebalanced without moving to the extreme upper end of balancing resistance I34. The amount of balancing resistance I34 left between its pper end and the balancing contact finger I38 will depend upon the amount of resistance 96 placed in circuit with the end of control resistance 82. As a result, the fresh air damper I3 will not be moved to its vertical positionbut will only be moved to a position approaching its vertical position whereby some flow of fresh air through the fresh air inlet duct II will be permitted. The amount of this minimum fresh air flow under hot weather conditions will depend entirely upon how much of the resistance 96 is manually placed in circuit with the control resistance 82.

Under excessive weather conditions, the cooling apparatus to be explained later may not be able to maintain the temperature of the space being controlled within the-desired limits if this minimum amount of fresh air is being taken in. If the outdoor temperature should continue to rise until it reaches some higher valuesuch as 85 F., the contact 9| will be moved into engagement with the switch arm 90. When this occurs, the effective portion of resistance 96 which has been manually placed in circuit with control resistance 82, will be shorted out by means of wire I41, switch arm 98, contact 9| and wire I48. Therefore, the short-circuiting of solenoid coil 18 will be just as complete as if none of this resistance 98 were in circuit with the control resistance 82. As a result, balancing contact finger I35 must move to the upper end of balancing resistance I34 before the solenoid coils I1 and I8 will again be substantially equally energized. It

therefore, follows, that fresh air damper I3 will be moved to its fully closed position.

To summarize the operation of the fresh air damper during the summer, this. damper is placed in a horizontal position in which a full flow of fresh air is permitted through the fresh air inlet duct when the outdoor temperature is 70 F. If the outdoor .temperature then falls 5 degrees to 65 F., this fresh air damper is moved to its closed position by moving in a counterclockwise direction. If, on the other hand, the outdoor temperature rises 10 degrees to this damper will be moved to its vertical position in which no flow of fresh air is permitted by F. to 80 F., or falls from 80 F. to 65 F., the Y fresh air damper is moved from a closed position to an open position and back to a closed position again. If it be desired to always take in a minimum supply of outdoor air, except under abnormal conditions, this can be done by manual manipulation of the rheostat 95. If themanually operable'rheostat is so manipulated. a minimum flow of fresh air will be maintained even though the outdoor temperature rises to 80 F., and theamount or volume of this minimum flow will depend upon the adjustment of manual rheostat 95. However, if the outdoor air temperature should become excessive by rising to F., the efiective portion of resistance 96 of the manually'operable rheostat will be short-circuited whereupon the fresh air damper will move to its full closed position just as if this manually operable rheostat had not been adjusted.

Whenever the outdoor temperature falls below- 65 F., and provided that the indoor temperature is below 75 F., the relay coil 28 of the changeover relay 25 will be deenergized as previously set forth. The system is thereupon operated upon the winter cycle instead of the summer cycle. Such deenergization of relay coil 28 causes swltcharm 23 to disengage contact 35. Thereupon, the contact arm' 31 of the rheostat contact 3! and this results in the control contact 83 being disconnected from the balancing contact finger I35 and from the junction of solenoid coils I1 and 18. The outdoor controller BI and the manually operable rheostat 95 therefore now have no effect upon the respective energizations of solenoid coils TI and 18. With switch arm 30 engaging contact 36,- the rheostat 98, the controller comprised by contact arm I and resist ance H0 and the protective resistance I39, all in series, are connected across or in shunt cir- 1 fresh air damper I 3 can be caused toassume a minimum open position at all times so that there will always be a small amount of fresh air taken into the air conditioning chamber I0 or the fresh cuit relationship with solenoid coil I1. This par- I allel or shunt circuit is as follows: starting with the junction of solenoid coils I1 and I8, wire I50, wire I5I, manual switch I49, wire I53, switch arm 30, contact 36, wire I60, contact arm I00, resistance 99, wire IBI, contact arm I08, sleeve II2 (with the parts in the position shown) wire I62, wire I38, protective resistance I39, and wire I40 to the left end of solenoid coil 11. It will therefore be noted that with the change-over relay 25 in its winter position, the control resistance 82 and manual rheostat 95 are disconnected from the solenoid coils I1 and I8 but that the balancing resistance I34 is still connected in parallel therewith. Also, it will be seen that the rheostat 98, the resistance H0 and the protective resistance I39, all in series, are connected in parallelwith the solenoid coil I1. This parallel circuit has just been described above and, with the manual contact arm I00 positioned as shown and with the temperature at 70 F., so that contact arm I08 is engaging the conducting sleeve I I2, very little resistance is in parallel with the solenoid coil 11 other than the protective resistance I39. 'It therefore follows that the solenoid coil I8 is more highly energized than the solenoid coil 11 whereupon plunger 15 moves to the right and brings switch arm 12 into engagement with contact 14. The auxiliary winding 80 and field winding 10, in series, are therefore energized by the circuit given above. Energization of field winding 10 causes rotation of main operating shaft 65 in counter-clockwise direction and such counter-clockwiserotation will continue until the balancing contact finger I has almost reached the lower end of balancing resistance I34 so as to rebalance the energizations of the solenoid coils I1 and I8. If none of the manual resistance 99 were in circuit with the solenoid coil 17, the'balancing contact finger I 35 would be moved to the extreme downward end of balancing resistance I34, but, with this small amount of resistance 99 connected in circuit with solenoid coil 11, the balancing contact finger I35 assumes a position which is quite close the lower end of balancing resistance I34. Rebalancing of the energizations of solenoid coils I1 and I8 causes the switch arm I2 to move away from contact I4 whereupon field winding I0 is deenerglzed and further rotation of main operating shaft 65 ceases. Such counter-clockwise rotation of main operating shaft 05 moves damper I3 in a counter-clockwise direction towards-its vertical position, and this damper I3 is thusmoved to a position in which itis nearly vertical and wherein only a small amount of fresh air is permitted to flow through the fresh air inlet duct II. It will, therefore, be seen that when the temperature of the room or space is at F., the fresh air damper I3 is positioned according to the adjustment of the manual rheostat 98. By the use of this manual rheostat 98, the

air damper I3 can be caused to move to its completely closed position, all depending upon the adjustment of this rheostat 90.

Suitable controls to be described later operate to maintain the space temperature constant in the winter, or within given limits. But if the temperature of the space to be controlled should rise for. any reason, the contact arm I08 will sweep across the conducting sleeve I I2 and when the indoor temperature has risen to 74 F., the contact arm I08 engages the extreme right end of the associated resistance IIO. If there should be a further increase in the indoor temperature, contact arm I08 will begin to move across the associated resistance IIO whereby a larger amount of resistance is placed in parallel with the solenoid coil 11. As a result, the energizations of the solenoid coils I1 and I8 will only be balanced when the balancing contact finger I35 is in a position further removed from the extreme downward end of balancing resistance I34. Under these conditions, the fresh air damper I3 is more widely opened. If the indoor temperature or the temperature of the space should for any reason rise to 78 F., then all of the resistance IIO will be placed in parallel with the solenoid coil 11. Under these conditions, the value of resistance III) is so chosen that the fresh air damper I3 wil1 be moved substantially to its horizontal position so that a full flow of freshair'is permitted through the fresh air inlet duct II.

By this arrangement, when the space tem-' perature is normal or is within a desired or permissible range of fluctuation, the fresh air damper I3 will be completely closed or may be positioned in a slightly open position by operation of the rheostat 98. But if the indoor or space temperature rises above this normal temperature, then the fresh air damper I3 is opened more and more widely until, at 78 F., this damp er is moved to its full open position. 'In' this manner,more and more fresh air is taken into the space to be controlled as'the temperature becomes excessive whereby to cause a lowering in such temperature.

The manual switch I49 provides for the manual moving of damper I3 to its full open position at any time, irrespective of whether the system be operating on a winter cycle or a summer cycle. When this manual switch I49 is opened, the junction of the solenoid coils I1 and I8 and the balancing contact finger I35 are disconnected from the contact arm 83 (if the apparatus be operating. on a summer cycle) or from the rheostat 98 and the contact arm I08 (if the system be operating on the winter cycle). As a result, none of these various control resistances or the manual rheostats are effective to vary the respective energizations of the solenoid windings I1 and I8. Their respective energizations are then controlled entirely by the balancing potentiometer I33. The energizations of solenoid coils I1 and I8 will'then only be equal when the balancing contact finger I35 is engagwhich is in control of the flow of fresh air to the air conditioning chamber, it will be readily appreciated that movement of this fresh air damper also indirectly affects the flow of air through return air duct I2. It is to be further understood that the usual cooperatively acting dampers in the fresh air and return air ducts could be used herein instead of the single damper.

Heating and humidifying control Turning now to Fig. 3 of the drawings, the heating coil 2I may be supplied with any suitable type of heating fluid and is herein shown as being supplied with steam from a steam supply pipe I which may be connected to a central power plant, district steam line, individual boiler or the like. The fiow of steam from the steam supply pipe I15 to the heating coil 2I is controlled by a valve I18. This valve I18 is in turn controlled by a motor mechanism generally indicated at I11. The motor mechanism I11 includes a main operating shaft I18 that drives a pinion I18 which in turn cooperates with a rack I88 that is secured to the valve stem I8I of the valve I18. This main operating shaft I18 is connected to a rotor shaft I82 through suitable reduction gearing indicated generally at I83. The rotor shaft I82 carries a pair of rotors I84 and I85 with which field windings I85 and I81 cooperate. The arrangement is such that energization of field winding I88 causes its associated rotor I84 to turn in one direction whereas energization of field winding I81 causes its associated rotor I-85 to rotate in the opposite direction. Therefore, the two rotors and their associated field windings constitute a reversible motor means- Energization of the field windings I88 and I81 is controlled by a switching mechanism that includes a switch arm I88 and a pair of com)- erating contacts I88 and I88. The position of switch arm I88 is controlled by a magnetic plunger I8I to which it is secured by a nonmagnetic and non-conducting connection I82.'

The position of plunger I8I is controlled primarily by a pair of normally electrically balanced oppositely acting solenoid coils I83 and I84. These solenoid coils I83 and I84 may be entirely separate or may be conveniently formed by providing a single coil with a center-tap. Theposition of plunger I8I is also additionally controlled, to a certain extent, by a pair of auxiliary windings I85 and I88.

Whenever solenoid coil I83 is more highly energized than solenoid coil I84 to a sufficient degree, switch arm I88 is moved into engagement with contact I88. When this occurs, auxiliary winding I85 and field winding I81, in series, are both energized, electrical power being furnished by the low voltage secondary I81 of a step-down transformer having a high voltage primary I88.

' ancing resistance 228 and wire 223 This series circuit for auxiliary winding I85 and field winding I81 is as follows: secondary I81, wire I88, wire 288, switch arm I88, contact I88,

wire 285, auxiliary winding wire 28I, winding I85, wire 282, field winding I81, wire 283 and wire 284 to the other side of secondary I81. Similarly, when the solenoid coil I84 becomes sufficiently more highly energized. than solenoid coil I83, switch arm I88 engages contact I88 whereupon the auxiliary winding I88 and the field winding I85, in series, are energized by a circuit as follows: secondary I81, wire I88, wire 288, switch arm I88, contact I88, I88, wire 288, field winding I86, wire 283 and wire 284 to the other side of secondary I81.

As stated above, the solenoid coils I83 and I84 are normally equally energized or electrically balanced. This is true since'the solenoid coils I83 and I84, in series, are connected directly across the secondary I81 by a circuit as follows: secondary I81, wire I88, wire 281, wire 288, solenoid coil I84, solenoid coil I83, wire 288 and wire 284 to the other side of secondary I81. The energizations of solenoid coils I83 and I84 are adapted to be primarily unbalanced by means of a potentiometer controller which comprises the control resistance H3 and cooperating control contact I88 of the controller I8I which was previously described in connection with the con trol of fresh air damper I3 (see Fig. 2). When the change-over relay 25 is in its winter position. this control resistance H3 is connected in parallel with the series connected solenoid coils I83 and I84 through a pair of protective resistances 2I8 and 2I I. This parallel circuit. is as follows:

from the right-hand end of solenoid coil I84,-

wire 288, wire 2I2, protective resistance 2I8, wire 2I3, wire 2I4, wire 2I5, control resistance II3, conducting sleeve II5, wire 2I8, wire 2I1, contact 48, switch arm 32, wire 2I8, wire 2I8 and protective resistance 2| I to the left-hand end of the solenoid coil I83. The energizations of solenoid coils I83 and I84 are adapted to be rebalanced irrespective of the particularcontroller or resistance which causes unbalancing thereof, by a balancing potentiometer which comprises a balancing resistance 228 and a balancing contact 22I which is driven by the main operating shaft I18. This balancing resistance 228 is permanently connected in parallel with the series connected solenoid coils I83 and I84, through the protective resistances 2I8 and 2I I by a circuit as follows: from the right-hand end of solenoid coil I84, wire- 288, wire 2I2, protective resistance 2I8, wire 2I3, wire 2I4, wire 222, balto the protective resistance 2H and the left-hand side of solenoid coil I83. Also, the balancing contact 22I is permanently connected to the junction of solenoid coils I83 and I84 by wires 224 and 225. The control contact I88 is connected to the junction of solenoid coils I83 and I84 when the change-over relay 25 is in its winter position by wire 228, wire 221, contact 38, switch arm 3I, wire 228 and wire 225.

The control contact finger I88 sweeps back and forth across the control resistance I I3 as the temperature of the space being controlled fluctuates between 70 F. and 74 F. as heretofore indicated. With the prevailing temperature at 70 F., if the change-over relay 25 is moved to winter position instead of the summer position shown,

,222,wire 2 I4, wire2I3, wire 2I2'a'rid wire288 solenoid; coil I94.

iary winding I88 and I94, wire 22!, wire 228, switch arm II, contact 38,,wire- 221, wire228'. controLcontact I 89, wire 2|, wire 2; wire-l2", protective resistance -2I8, wire 2I2, and'wire 288 to the righthand end of solenoid coil I84.: This solenoid coil, I94 is also substantially 'shortqcircuited by This energizati'on of the auxiliary winding I95 causes an additional magnetic force to be applied to the plunger I9I, tending to move the sameto the ,left.. This-brings switch arm I88 into more firm: engagement with contact I89. Eners'ization of field winding I81 causes rotation of main operating shaft I18 in a clockwise direction as viewed from the left whereupon the rack I88 is raised and the valve I16 is moved toward open position. This clockwise rotation of main operating shaft I18 will ancing contact 22I has completely traversed the balancing resistance 228 and is engaging the wire 223. When this occurs, the solenoid coil I93 is substantiall short-circuited, complete shortcircuiting being prevented by the protective resistance 2. This circuit is as follows; from the junction of solenoid coils I93 and I94, wire 225, wire-224, balancing contact finger 22I, wire 223 and protective resistance 2I I to the left-hand end. of solenoid coil I93. The energizations of solenoid coils I 93 and I94 are now substantially equalized and the plunger I 9| sufiiciently far to separate switch arm I88 and contact I89. Separation of this switch arm and associated contact interrupts the series circuit through the auxiliary winding I95 and the field winding I81. Deenergization of the auxiliary winding I95 removes the auxiliary attractive force tending to move plunger I9I towards the left, whereupon plunger I9I moves to its central position or further to the right so as to widely separate the switch arm I88 and the contact arm I89, thereby assuring a good clean break. Further rotation of main operating shaft I18, of course, ceases upon the deenergization of the field winding I 81. The steam valve I16 is now completely open and a maximum flow of steam is permitted to the heating coil 2| whereby to heat the air chamber I8.

' Now, as the space temperature rises as a result this heating action, the control contact I89 moves along the control resistance I I3 towards its left-hand end. As this movement takes place, part of the control resistance I I3 isplaced in the shunt circuit above described for the solenoid coil I94, which shunt circuit formerly included only the protective resistance 2| 8, This placing of further resistance in this circuit, increases the fiow of current through the solenoid coil I94. The solenoid coil I93, however, remains substantially short circuited since the balancing contact finger 22I is at the extreme upper end of balancing resistance 228 andis engaged with the wire 223. Plunger -I9I therefore moves to passing through the air conditioning reasonoi' the fact that the balancing contact continue until the balmoves to the right I causes counter-clockwise rotation that has just been placed in this circuit has become suiiiciently large, plunger I9I will move far enough to the right to. bring switch arm Ill into engagement with contact I98. Thereupon the a winding I96 and the field winding I86, in series, are energized by the circuit formerly traced. This energization of I96 causes a further attractive auxiliary winding I I9I, tending to force to be applied to plunger move thesame to the right whereupon switch arm 188 is moved into.firm engagement with contact I88. Energization ofiield winding I86 of main operating shaft I18 as viewed from the left. This counter-clockwise rotation of main operating shaft-I18 moves rack I88 downwardly to partially close valve I16 and also moves balancing contact 22I along balancing resistance 228 away from its upper end and towards its lower end. As the balancing contact 22I thus moves along balancing resistance 228, part of the balancing resistance 228 is placed in the formerly described shunt circuit for the solenoid coil I 93 whereby the current flow therethrough is increased. When the balancing contact 22I has moved sufficiently far along balancing resistance 228, the energizations of solenoid coils I93 and I94 will be sumciently nearly equalized to cause plunger I9I to move suillciently far to the left to separate contact arm I88 and contact I98. The auxiliary winding I96 and the field winding I86 are thereupon deenergized. Deenergization of auxiliary winding I96 removes the supplemental force tending to move plunger I9I' towards the right whereupon the contact arm I 88 moves further away from the contact I88 and causes a good clean break. The deenergization offield winding I86 results in stopping of the main operating shaft I18. The valve I16 is now partially closed.

If the temperature of the space to be controlled should rise to 74 F., then the control contact I89 will engage the conductive sleeve II 5. Under these conditions, the-solenoid coil I93 will be substantially short-circuited irrespective of the position of the balancing contact 22I in relation to the balancing resistance 228. This substantial short circuit for the solenoid coil I93 is as follows: from the junctionv of solenoid coils I93 and I 94 wire 225, wire 228, switch arm 3|, contact 38', wire 221, wire 226, control contact I 89, conductive sleeve tact 48. switch arm 32, wire 2I8, wire 2I9 and protective resistance 2 to the left-hand end of solenoid coil I93. The plunger I9I again moves to the right and switch arm I88 moves into engagement with contact I98 whereupon the auxiliary winding I 96 and field winding ,I 86 are againenergized. The main operating shaft I18 is again rotated in a counter-clockwise direction to move valve I18 in a closing direction and to move balancing contact 22I along balancing resistance 228 towards its lower end. The energizations of solenoid coils I 93 and I94 will not now be substantially equallized until the balancing contact 222 that connects with of balancing resistance it is engaging the wire the extreme lower end 228. When the balancing contact 22I reaches the right and when the amount of resistance-H3 this position, the solenoid coil I94 will be substantially short-circuited by the shunt circuit formerly described; Thereupon, the plunger I9I will move switch arm I88 from engagement with contact I98 and the auxiliary winding I 96 and the field winding I88 will again be deenergized.

he valve I16 is now fully closed.

II5, wire 2I6, wire 2", con

tem is operating on a winter cycle. the steam valve 234 cooperating insulation 248. The

,trical power is furnished is taking place as It will therefore be seen that with the apparatus thus far described, the steam valve I15 is moved from full open position to full closed posi-' tion as the temperature of the space being controlled rises from 10 F. t 74 F. whenthe sys- Similarly, l15-is moved from its full closed position to its full open position as the space temperature being V controlled falls from 14 F. to 70 F.

The system of the present templates controlling the relative humidity of the air in the space during the winter by'adding water to the air passing through the air conditioning chamber 15 whenever the relative humidity falls below a desired point. Further, the present invention contemplates varying the relative humidity maintained in this space upon fluctuations of the outdoor temperature, in such a manner that the value of the relative humidity in the space is lowered as the outdoor In this manner, values of relative humidity are maintained such that the dew point the air is always below the temperature of exposed windows and walls whereby condensation thereon is prevented.

In order to accomplish these functions, water is furnished to the spray 22 from any suitable source, herein indicated as a water supply pipe 239. The flow of water from the water supply pipe 239 to the water spray 22 is controlled by a solenoid valve 23i. valve 23l is controlled by a relay mechanism generally indicated at 232. This relay mechanism 232 includes an energizing coil 233 and a neutralizing or bucking coil 234, these two coils 233 and in the control of an armature 235. Armature 235 controls a pair of switch arms 235 and 231' that respectively cooperate with contacts'238 and 239. Switch arm 231 and its coopcrating contact 239 control a circuit to solenoidv valve 231 which is as follows: line wire 245, contact 239, switch arm 231, wire 24!, solenoid valve BI and line wire 242. It will therefore be apparent that whenever switch arm 231-engages contact 239, solenoid valve 23i is energized to permit the flow of waterfrom water supply pipe 239 to the water spray 22.

The relay mechanism 23.2-is controlled by a relay mechanism 243 which includes a pair of oppositely acting solenoid coils 244 and 245 that cooperate in the positioning of a single pivoted armature 245. Armature 245 controls a switch arm 241 to which it is secured through a piece of switch arm 241 cooperates with a pair of contacts 249 and 255. Whenever switch arm 241 engages contact 249, the energiz-- ing coil 233 of relay mechanism 232 is energized, provided that-electrical power is available. Elecby a transformer having a low voltage'secondary 251 and a high voltage primary 252. This primary 252 is energized whenever the change-over relay mechanism 25 is in its winter position. This circuit is as follows: line wire 253, switch arm 23', contact 33, wire 254, primary 252 and wire 255 to ground 255. Therefore, assuming that winter operation has been assumed above in this part of the description, the engagement of switch arm '2" with contact 249 causes energimtion of "energizing coil 233 by a circuit as follows: secondary 251, wire 251, wire 253, wire 259, energiz ing coil 233, wire 249, wire 251, wire side of secondary 25!.

to the other this en- 252 and wire 253 Energization of invention also contemperature falls.

Energization of the solenoid that cooperates 259, switch am 241, contact ing coil 241, wire 259, wire 254, contact 238, switch arm valve 23l as previously described. Engagement of i switch arm- 235 with contact 238 establishes a holding circuit for energizing coil 233 which is entirely independent of switch arm tact 249. This holding circuit is as ondary 25l, wire 251, wire 258, wire 259, energizing coil 233, wire 254, contact 238, switch arm 235, wire 252, and wire 253 to the other side of secondary 251 Therefore, the energizing coil 233 remains energized even though the switch arm 241 disengages contact 249. Now, whenever switch arm 241 engages contact 259, a circuit for the secondary 25l wire251, wire 258, wire 255, buck- 234, wire 255, contact 255, switch arm follows: sec- 235, wire 252, and wire 253 to the other side of secondary 25i. The magnetic effect produced by bucking mum neutralizes the magnetic effect produced by energizing coil 233, whereupon armature 235 is free to move to its normal biased position wherein switch arms 235 and 231 are disengaged from their respective contacts 233 and 239. The solenoid water valve 231 is thereupon deenergized. Disengagement of switch arm 235 from contact 238 not only interrupts the holding circuit for the energizing coil 233 but also interrupts the circuit for bucking coil 234 so that both of these coils are now deenergized and the parts remain in the positions shown. Armature 235 will now remain in its biased position until switch arm241 again engages con'tact249 whereupon the above described operation will be repeated. As a result, solenoid water valve 231' is opened whenever switch arm 241 engages. contact 249 and is maintained open until switch arm 241 subsequently engages contact 255. I

The solenoid coils 244 and connected across secondary 25L This as follows: secondary 25l, wire 251, wire 245, in series, are

wire 258, solenoid coil 244, solenoid coil 245, wire 259, wire 219 and wire 253 to the other side of secondary 25L Variations in the energizations oi the respective solenoid coils 244 and 245 are adapted to be produced primarily by a potentiometer controller that is actuated in response to relative humidity changes in the room or space. This humidity responsive troller comprises a bell crank which is pivoted at 219 and includes an arm 21l. This arm 2" is connected to a humidity responsive element 212 which is herein shown as comprised by a plu rality of strands of hair. The otherend-of this element 212 is secured as indicated at 213, A coiled tension spring 214 operates to maintain element 212 under proper tension at all times. The bell crank is provided with a second arm 215 which takes the form of a control contact with a control resistance 215. The arrangement is such that the control con-. tact 215 completely traverses the control resistance 215 upon a predetermined change in relative humidity which, for the purpose of the present explanation, has been selected as changes in humidity ranging from 20% to 40%. With the parts in the posit on hown, 'the relative humidity is 40% so that the control contact 215 is engaging the extreme right-hand end of control resistance 215. This control resistance 215 is connected in parallelwith the series connected 241 and conbucking coil 234 is established as follows:-

circuit is potentiometer consolenoid coils 244 and 245, the left end of control resistance 216 being connected to the lower end of solenoid coil 245 by wire 21'! and wire 268, the right-hand end of this control resistance 216 being connected to the lower end of solenoid coil 244 by wire 218, wire 219, and wire 268. The control contact 215 is connected to the junction of solenoid coils 244 and 245 by wires 280 and 28!.

With the parts in the position shown, except that assuming the change-over relay 25 is in its winter position, the secondary 251 is energized and the solenoid coil 244 is short circuited by the following circuit: from the junction of solenoid coils 244 and 245, wire 281, wire280, control con-'- tact 215, wire 218, wire 219, and wire 268 to the lower end of solenoid coil 244. As a result, under these conditions, solenoid coil 245 will be more highly energized than solenoid coil 244' whereupon switch arm 241 is moved into engagement with contact 258. Under these conditions, the relay armature 235 of the relay mechanism 232 will be in the position shown in Fig. 3. Therefore, water valve 23! will be deenergized. If the relative humidity of the room or space should now begin to lower so that control contact finger 1 1 whereupon solenoid valve 23| is deenergized and the supply of water to the water spray 22 is discontinued, In this manner, the relative humidity responsive controller operates to turn on and off the water supply to water spray 22.

As pointed out above, the present invention includes means for varying the relative humidity that is maintained in the room or space upon fluctuations in outdoor temperature. For this purpose, an outdoor temperature responsive controller generally indicated at 285 is utilized. This controller includes a rotatable shaft 286 to which an arm 281 is secured. This arm is operated by a pressure responsive device 288 in the form of 215 moves along the control resistance 216 towards its left-hand end, part of the resistance 216 will be placed in the shunt circuit for solenoid coil 244. Likewise/ some of the-resistance 216 will be removed from a shunt circuit for solenoid coil 245 which is as follows: from the junction of solenoid coils '244 and 245, wire 2!, wire 288, control contact 215, control resistance 216, wire 211 and wire 269 to the lower end of solenoid coil 245. As a result, the difference in the energizations of solenoid coils 244 and 245 is reduced as the control contact 215 approaches the center of control resistance 216. When the control contact 215 has reached the center of controlresistance 216, there will of resistance 216 in the shunt circuits for solenoid coils 244 and 245 whereupon they will be be equal amounts equally energized and the switch arm 241 will I be disposed exactly intermediate the contacts 248 and 250. As the relative humidity continues to lower so that cotnrol contact 215 moves past the center of control resistance 216 while moving towards the left-hand end thereof, more than half of the control resistance 216 will be placed in parallel with 'the solenoid 244 and less than half thereof will be placed in parallel with the solenoid 245. The solenoid coil 244 thereupon becomes more highly energized than the solenoid coil 245 and, when this difference in energization is sufficient, switch arm 241 will engage contact 249 whereupon the water valve 23I will be energized through the relay mechanism 232 as previously described. Then, if the relative humidity rises to again equalize the energizations of solenoid coils 244 and 245, or to reduce the difference between such energizations, the switch arm 241 will disengage the contact 248, However, the solenoid valve 23l remains energized by means of the holding circuit for the energizing coil 233 of the relay mechanism 232. Then, as the relative humidity continues to rise and goes above 30% so that the control contact finger 275 moves past the'center of control resistance 216 and towards the right-hand end thereof. solenoid coil 245 becomes more highly energized than solenoid coil 244. When this difference in energizations has become sumciently great, switch am 241 engages the contact 250 to energize the bucking coil 234 of the relay mechanism 232 a bellows which is connected to a controlling bulb 289 by means of a connecting tube 290. The bellows 288, controlling bulb 289, and connecting tube 290 are charged with a suitable amount of volatile'or expansible fluid whereby the pressure in bellows 288 increases upon temperature rise. The action of the bellows 288 'is opposed by a suitable tension spring 2! in the usual manner. The bulb 289 responds to outdoor temperature and may be conveniently located in the fresh air intake duct H. The shaft 286 supports a pair of control contacts 292 and 293. The con trol contact 292 cooperates with a control resistance 294 for a purpose to be hereinafter set out, and control contact 293 cooperates with a similar control resistance 295. The arrangement is such that the control contacts 292 and 293 completely traverse resistance 294 and 295 upon forty degrees change in outdoor temperature, the range in this particular embodiment of the invention being from 0 F. to 40 F. Inasmuch as the outdoor temperature will often rise above 40 F., the control-contacts 292 and 293 are arranged to ride upon conductive sleeves 296 and 291 after they have completely traversed the control resistances 294 and 295 upon temperature rise.

The control resistance 295 is connected in parallel with thecontrol resistance 216, the lefthand end of both of these resistances being inter-connected by a wire 298 and the righthand ends thereof being inter-connected by wire 218 and a wire 289. The control contact 293 is connected to the junction of wires 280 and 28! by a wire 380. When the control contact 293 is engaging the center of the associated control resistance 295, that is at 20 F. outdoor temperature, then the humidity controller will operate to maintain the relative humidity of the space at about 30%, since it will also control from the center of control resistance 216. How ever, if the outdoor temperature rises somewhat, say to 30 F., then more of the control resistance 295 will be in parallel with the solenoid coil 244 'a lower degree of average relative humidity is maintained therein. By this arrangement, as

. the outdoor temperature lowers, the relative humidity in thisspace is maintained at lower and lower values so that the dew pointtemperature of the air in the space is always kept below the temperature of the windows and the exposed to the junction of wires 226 and 221 by walls whereby to prevent the condensation of moisture thereon.

Since the relative humidity is thus allowed to fluctuate upon changes in-outdoor temperature, although the dry bulb temperature is maintained constant by the apparatus 'hereinbefore described, such fluctuations in relative humidity will cause fluctuations in the effective temperatures of the space. The present invention, therefore, contemplates adjusting the dry bulb temperature in the space in accordance with the fluctuations in the relative humidity so as to maintain the effective temperature substantially constant at all times. In order to accomplish this result, the control potentiometer comprised by the control contact 292 and the control resistance 294 is associated with the indoor temperature controller comprised by the control contact I09 and the control resistance II3. It will be noted that the right-hand end of the control resistance 294 is connected to the righthand end of solenoid coil I94 by being connected to the wire 2I3, by a wire 385. Similarly, the left-hand end of control resistance 294 is connected to the left-hand end of solenoid I93 by being connected to the junction of wires 2 I8 and 2I1 by a wire 388. The control resistance 294 is therefore connected in parallel, through protective resistances 2III and 2I I, with the seriesconnected solenoid coils I93 and I94. The control contact-292 is, connected to the junction of solenoid coils I93 and I94 by being connected a wire 301. As a result, when the outdoor temperature is at a value of 20F. so that the control contact 292 is engaging the center of control resistance 294, then half of this control resistance is in parallel with the solenoid coil I93 and half of it is in parallel with solenoid coil I94. Under these conditions, the control resistance 294 and its associated control contact 292 has no effect upon the position the main operating shaft I18 will assume under the influence of the controller comprised by control resistance I I3 and its associated control I99. However, if the outdoor temperature should rise to 30 F. so that a higher relative humidity is thereupon maintained in the space as heretofore set out, then less of the resistance 294 is placed in parallel with the solenoid coil I93 so that the current thereto increases ?and the balancing contact finger 22I must move further towards the lower end of balancing resistance 228 before the energizations of the solenoid coils I93 and I94 are again balanced. As a result, the steam valve is closed down somewhat so that a lower space temperature is maintained. This lowered space temperature taken together with the higher space relative humidity maintains the effective temperature of the space constant or substantially so. The opposite action takes place upon a decrease in the outdoor temperature so the final result is that the relative humidity maintained in the space is varied upon changes in outdoor temperature but the dry bulb temperature of the space is thereupon varied so as to maintain the effective temperature in the space constant at all times. This control therefore provides for a comfortable control of the space at all times while retaining the relative humidity at the safe value.

With the parts in the position shown as in Fig. 3, the change-over relay 25 is energized and the apparatus is operating on a summer cycle. Under these conditions, the transformer secondary 25I is deenergized since switch arm 28 is disengaged sis provided the changethat is pivoted at 339. The

from contact 33. As a result, neither of the solenoid coils 244 or 245 is energized and the contact arm 241 is intermediate contacts 249 and 250 as shown. Also, irrespective of the last operation of the relay mechanism 232, both the energizing coil 233 and'the bucking coil 234 are now deenergized so that the switch arm 231 is disengaged from its cooperating contact 239 and the solenoid water valve 23I is deenergized. Furthermore, the control contacts292 and I09 are disconnected from the junction of solenoid coils I93 I vand l94 since switch arm contact 38. Likewise, the left-hand end of the control resistances H3 and 294 are disconnected from the left-hand end of solenoid I93 since switch arm 32 is disengaged from contact 48. Also, the. solenoid I93 is substantially short-circuited by a shunt circuit which is as follows: from the junction of coils I93 and I94, wire 225, wire 228, switch arm 3I, contact 39, wire 3I0, switch arm 3I I, a cooperating contact 3I2, wire 3I3, contact 4I, switch arm 32, wire 2I8, wire 2I9 and protective resistance 2I I to the left-hand end of solenoid coil I93. As a result, balancing contact finger 22I is in the position shown wherein the solenoid coil I94 is substantially short-circuited by the circuitas traced above. Under these conditions, the steam valve I18 is closed, as will be evident, and, of course, this is the proper position for the steam valve during the summer operation.

Cooling and dehumidifying control Referring to Fig. 1, the dehumidifying coil I9 and the cooling coil 20 may be supplied with any suitable type of coolin and are herein shown as being supplied with liquid refrigerant by meansof a mechanical refrigeration system that includes a compressor 3I5 and a condenser 3I5, The compressor 3I5 is driven by a compressor motor 3". The flow of the liquid refrigerant from the condenser 3; to the cooling coil 20 is; controlled entirely by an expansion valve 3I8 but the flow of liquid refrigerant from the condenser 3I6 to the dehumidifying coil I9 is controlled not only by an expansion valve 3I9 but is also controlled by a solenoid valve 328. As a result, whenever liquid refrigerant is available, it may flow to the cooling coil 28 under the control of its expansion valve 3I8 but it can only flow to the dehumidifying coil I9 under the control of the expansion valve 3I9 in the event the solenoid refrigerant valve 320 is open. vliinergization of the compressor motor 3" is controlled by the summer-winter changeover relay 25 and in part by a relay mechanism 32I. This relay mechanism 32I includes an energizing coil 322, a bucking coil or neutralizing coil 323 and an armature 324. The armature controls a pair of switch arms 325 and 326 which cooperate with contacts 321 and 328. Whenever the switch arm 326 engages the contact 328', and over relay 25 is in summer positio as shown, so that its switch arm 28 is engaging contact 34, the compressor motor is energized by the following circuit: line wire 253, switch arm 28, contact 34, wire 329, wire 330, wire 33I, contact 328, switch arm 328, wire 332, wire 359, compressor motor 3", and wire 333 to ground 256.

The relay mechanism 32I is controlled by a relay mechanism 335 that includes a pair of oppositely acting solenoid coils 336 and 331 that cooperate in the control of a single armature 338 armature 338 con- 3I is disengaged from or refrigerating medium.

'trols a switch arm 343 through a piece of However, whenever switch contact 343,

ture responsive device,

asoacu insu lation 3 and this switch arm 343 cooperates with a pairof spaced contacts 342 and 343. Whenever the switch arm 343 engages the contact 342, energizing coil 322 of relay mechanism 32l is energized, provided power is avaflable.

Power is furnished by the low voltage secondary 344 of a transformer having a high voltage primary 345 which is energized whenever the change-over relay 25 is in summer position. This energizing circuit for primary 345 is as follows: line 'wire-253, switch arm 28, contact 34, wire 329, wire 346, primary 345 and wire 341 to ground 256. Therefore, assuming-switch arm 343 engages contact 342, energizing coil 322 is energized as follows: secondary 344, wire 348, wire 349,

energizing coil 322, wire 350, switch arm 343, contact 342, wire 35l, wire 334 and wire 352 to the other side of secondary 344. Energization of the energizing coil 322 attracts the armature- 324 and causes switch arms 325 and 325 to be moved into engagement with their' respective contacts 321 and 328. Engagement of switch arm 326 with contact 323 energizes the compressor motor 3" by the circuit set forth above. The engagement of switch arm 325 with contact 321 establishes a holding circuit for energizing coil 322 which is entirely independent of the switch arm 340 and the contact 342, this holding circuit being as follows: secondary 344, wire 348, wire 349, energizing coil 322, contact 321, swticli arm 325, wire 353 and wire 352 to the 344. Energizing coil 322 will now remain energized if switch arm 343 disengages contact 342.

7 am 343 engages contact 343, the bucking coil 323 will be energized by a circuit which is as follows: secondary 344, wire-343, wire 354, bucking coil 323, wire 355, switch arm 343, wire 353, contact 321, switch arm 325, wire 353 and wire 352 to the other side or secondary 344. The magnetic eii'ect produced by the bucking coil 323 neutralizes that, produced by'the energizing coil 322 whereupon the armature 324 returns to the position shown wherein switch arms 325 and 326 are disengaged from contacts 321 and 328, Disengagement of switch arm 326 from contact 328 deenergizes compressor motor 311. Disengageother side of secondary 1 3 bell crank that is pivoted at m and includes an am 332 that is positioned by a pressure responsive member herein shown as a bellows 363. This 'bellows'is connected to a suitable control bulb 364 by means of a connecting tube 335. The bellows 363, the control bulb 364 and the tube 365 are charged with a suitable amount of volatile or expansible fluid whereby the pressure in bellows 363 is increased upon temperature rise. The pressure in the bellows 363 is opposed by a coiled tension spring 366 in the usual manner.

The bell crank which is pivoted at 36! includes a second arm 361 which-takes the form of a control contact that cooperates with a control resistance 363. In this particular embodiment oi the invention, the arrangement is such that the control contact 361 traverses the control resistment of switch arm 325 from contact 321 interrupts the holding circuit for energizing coil 322 as well as the circuit for bucking coil 323 whereby neither of these coils is longer energized. The armature 324 will therefore remain in the position shown until switch arm 343 again engages contact 342.

The respective energizations of solenoid coils 336 and 331 of the relay mechanism 335, and therefore the energization and deenergizationof the compressor motor 3", are controlled by the cooperative action of a space dry bulb temperaa space relative humidity responsive device, and an outdoor dry bulb temperature responsive device. The arrangement is such that the indoor relative humidity responsive device and the space dry bulb temperature responsive device cooperatein such a manner as to maintain the eilective temperature of the ance 363 upon temperature changes ranging from 70 F. to 82 F. As noted above, this controller responds to the space temperature and its cona trolling bulb 364 may be conveniently placed in the return air duct l2.

The relative humidity responsive controller is indicated generally at 310 and comprises a bell.

crank pivoted at 3" which includes an arm 312 that is secured to one end of a humidity responsive element 313. This humidity responsive element may take any desired form and is herein shown as comprising a plurality of strands of hair. The other end of element 313 is suitably secured as indicated at 314. A coiled tension spring 315 serves to keep the humidity responsive element 313 at the proper tension. This bell crank includes a further arm 316 which takes the form of a control contact that cooperates with a control resistance 311. The arrangement is such that the control contact 3.16 sweeps across the control resistance 311 upon changes in relative humidity ranging from 30% to and, in.

accordance with'the disclosures of the other figurcs of the drawings, this controller is shown in the position it assumes when the prevailing relative humidity is substantially 40%.

The outdoor temperature responsive controller is generally indicated at 333 and comprises a rotatable shaft 33! to which an arm 382 is secured. This arm 332 is positioned by a pressure responsive device in the form of a bellows 333 that is controlled by a control bulb 334 to which it is connected by means of a tube 335. The bellows 333, controlbulb 334 and the tube 385 are charged with suitable volatile or expansible fluid so that the pressure in the bellows 383 increases upon temperature rise. In order 'to make this apparatu respond to outdoor temperature, the bulb 334 may be located in any convenientplace and is herein shown as located in fresh air inlet I I. The pressure in the bellows 333 is opposed by v a suitable coiled spring 336 in the usual manner.

The shaft 33l supports three control contacts 333. These three control contacts 388, respectively, cooperate with 331. 333 and 331, 333 and three compensating resistances 393, 39l and 392.

,The arrangement is such that each of these control contacts completely traverses its 1 associated resistance upon changes in outdoor temperatures, ranging from F. to F. I

The solenoid coils 336 and 331, in series, are connected across the secondary 344 by the following circuit: secondary 344, wire 395, wire 396, solenoid coil 333, solenoid coil 331, wire 391, wire 334, and wire 352 to the other side of secondary 344. The control resistances 311 and 358, in parallel, are connected in parallel with the seriesconnected solenoid coils 336 and 331, through tion of solenoid coils 336 and 331 by a wire 401.

With the parts in the position shown wherein the inside and outside temperatures are substantially F., and the inside relative humidity is approximately 40%, the relay coil 331 is more highly energized than the relay coil 336 and switch arm 34!! is engaging contact 343 so that relay mechanism 32l is deenergized and the compressor motor 3|1 is also deenergized and no cooling is taking place. In order to simplify the explanation of this particular phase of the system, let it be assumed that the outside temperature is half way between the range of controller 380 or is at approximately 8'1 F., andthat the relative humidity in the space is 45%. Under 'these conditions, none of the resistance 391 and one-half of each of the resistances 390 and 392 will be included in the various shunt circuits for relay coils 336 and 331 that will shortly be described. Also, under these assumed conditions, the contact arm 316 of the relative humidity re-. sponsive controller 310 is engaged with the midportion of its associated resistance 311. Also, assume that the space temperature is intermediate 10 F. and 82 F. or substantially 76 F. so that the contact 361 is engaging the center of its associated resistance 368.

Under these assumed conditions, it will be evident thatj-relay coils 336 and 331 are equally energized. It will be noted that there is a shunt circuit for relay coil 336 that includes half of each of resistances 311 and 368 in parallelv and includes half of resistance 390 in series therea with. This shunt circuit is as follows: from the junction of solenoid coils 336 and 331, wire 401,

contact 388 and wire 406 whereupon the circuit branches, one portion going by way of wire 4 05, contact 361 and the left-hand portion of resistance 368 towire399, whereas the other branch of the circuit goes by way of wire 404, contact .316, the right-hand half of resistance 311, and

wire 400 to wire 399, after which the circuit joins and goes through half of resistance 390, contact 381, wire 398 and wire 396 to the lower end of solenoid coil 336. There is a similar shunt circuit for solenoid coil 331 which includes half of each of the resistances 311 and 368 in parallel and half of resistance 392 in series therewith. This shunt circuit is as follows: from the junction of solenoid coils 336 and 331, wire .401, contact 388 and wire 406, whereupon the circuit branches part going by way of wire 405, contact 361 and the right? hand half of resistance 368 to wire 402, whereas the other portion goes by way of wire 404, contact 316, the left-hand half of resistance 311 and wire to wire 402 after which the circuit traverses half of resistance 392, contact 383, wire 403, wire 334 and wire 391 to the lower end of solenoid coil 331. These solenoid coils 336 and 331 are therefore equally energized and the switch arm 340 will be disposed intermediate contacts 343 and 344. Assuming that switch arm 340 was last engaged with contact 343,-then the relay mechanism 321 and compressor motor 3" will be deenergized.

Now if the. temperature of the space should rise slightly so that the contact 361 moves alon the associated control resistance 368, towards its right-hand end, more of resistance 368 will be placed in the shunt circuit for solenoid coil 336 and less of the resistance 368 will be contained in the shunt'circuit for solenoid coil 331.v As a result, more current flows through solenoid coil 336 and less through solenoid coil 331 so that switch arm 340 moves towards contact 342. When this rise in space temperature has been sufficient, switch arm 340 will engage contact 342 whereupon energizing coil 322 will be energized by the circuit described above. Switch arm 326 therefore engages contact 328 to energize compressor motor (ill by the previously described circuit whereupon refrigerant is delivered to the cooling coil 20 through the associated expansion valve 3I8. The air being delivered to the space will therefore begin to cool and. contact 361 will move to the left along its associated control resistance 368.

Switch arm 340 will therefore disengage contact 342 but the energizing coil 322 will remain energized by the holding circuit set forth above. when the temperature of the space again reaches 76 F., switch arm 340 will be exactly intermediate contacts 342 and 343. Further drop in space temperature places less of resistance 368-in the shunt circuit for solenoid coil 336 and more of resistance 368 in the shunt circuit for solenoid closer to contact 343 and when this temperature drop has been suflicient, the switch arm 340 will engage contact 343. Engagement of these parts energizes the neutralizing coil 323 as previously explained and switch arm 326 disengages contact 328 to deenergize the compressor motor 3" to discontinue the refrigerating action as soon as the compressed refrigerant is used up.

It will thus be seen that for the assumed conditions of 87 /2 F., outdoor. temperature and 45% relative humidity, the inside controller 360 will control the relay mechanism 335 to maintain the space temperature .at substantially 76 F.

If the relative humidity should now fall to 40% as shown in Fig. 1 of the drawings, less of resistance 311 will be contained in .the shunt circuit for solenoid coil 336 and more of this resistance will be contained in the solenoid coil 331. As a result, the energization of solenoid coil 336 will be reduced and that of solenoid coil 331 will be increased wherefor the space temperature must rise somewhat above 76 F. so as to bring more of resistance 368 in the shunt; circuit for solenoid coil 336 and less resistance for the solenoid coil 331 in order to bring about a balanced energization of these solenoid coils. As a result, lowering of the relative humidity of the space shifts the control point of the controller 360 so that a. higher space temperature will be maintained. On the other hand, an increase in the space relative humidity causes the opposite action by placing less of the resistance 311 in the shunt circuit for solenoid coil 336 and more of this resistance in the shunt cir- It will thus be seen that a decrease in relative humidity causes a higher space temperature to be maintained and an increase in relative humidity causes a lower temperature to be maintained wherefor the effective temperature of the space is maintained constant or. within desired limits.

In a similar manner, if the outdoor temperature should fall below 87 /2" F., more of the resistance 390 will be placed in the shunt circuit cult for solenoid coil 331 420, switch arm 4|8, wire contact 34, wire 428, primary 421 bring contact arms 4H! and for solenoid coil 336 and less of resistance 362 will be contained in the shunt circuit for solenoid coil 331. The solenoid coil 336 therefore becomes more highly energized and the energiza tion of solenoid coil 331 is reduced. The space temperature must therefore fall to a lower degree so as to remove part of the resistance 368 from the shunt circuit of solenoid coil 336 and place more of this resistance in the shunt cirin order to again equalize the energizations of these solenoid coils. As a result, a lowering of outside temperature shifts the control point of the controller 360 so that a lower space temperature is maintained. The

opposite action takes place upon an incease in the outside temperature so that a higher space temperature is maintained.

The values of the resistances as well as the ranges of these various controllers is preferably such that the effective temperature maintained in the space by the cooperative action of the controllers 368 and 310 is raised at a slower rate than the outdoor temperature rises so that a variable differential is maintained between the inside effective temperature and outdoor dry bulb temperature.

In the event the relative humidity should reach 60%, a pair of switch arms 4| and 4 are sequentially moved into engagement with a pair of cooperating contacts 4| 2 and 4| 3. The arrangement is such that switch arm 4| 0 first engages contact M2 and then switch arm 4 engages contact 4I3. These switch arms and contacts control arelay generally indicated at MS which in turn controls the refrigerant solenoid valve 328. This relay mechanism 4|5 com.- prises a relay coil M6 and a cooperating armature M1. The armature 4|1 controls the switch arm 8| I, hereinbefore mentioned, and also controls switch arms M8 and M9. Switch. arm 4| 8 cooperates with contacts 351 and 420 and switch arm 4I9 cooperates with a contact 42I. Switch arm M8 and its cooperating contacts 351 and 420 control circuits through the compressor motor 3H and the solenoid refrigerant valve 320. The circuit for compressor motor 3|1 is as follows: line wire 253, switch arm 28, contact 34, wire 329, Wire 3311, wire 422, wire 423, contact 420, switch arm 4| 8, contact 351, wire 358, wire 359, compessor motor 3|1 and wire 333 to ground 256. The circuit for solenoid valve 326 is as follows: line wire 253, switch arm 28, contact 34, wire 324, wire 330, wire 422, wire 423, contact 424, solenoid valve 328 256. Itwill be noted completed only when and wire 425 to ground that these circuits can be t'ure is not as low as ,1 5 which will appear hereinafter) moves switch arm 4|8 into engagement with contacts 420 and 361, and moves switch arm 9 into engagement with contact 42I. Engagement of switch arm 4I8 with contacts 426 and 361 opens the dehumidifying solenoid valve 328 and energizes compressor motor 3". Movement of switch arm 4|8 into engagement with contact 42I establishes a ho1ding circuit for relay coil 6 which is independent of the contact arm 4 holding circuit is as follows: secondary 426, wire 430, contact 2, contact arm 4| 6, wire 434, contact 42I, switch arm 4|9, relay coil 6 and wire 432 to the other side of secondary 426. The relay coil 4|6 will therefore remain energized until the relative humidity drops sufiiciently not only to disengage contact arm 4 from contact 4I3 but also to disengage contact arm 4|0 from contact 4 I2. The resulting flow of refrigerant to the dehumidifying coil I6 causes the air'passing thereover to be cooled below its dew point whereby moisture is removed therefrom. This may be accomplished by design of the coil I9 or through the setting of the expansion valve 3|9. While refrigerant will also flow to cooling coil 2p, this will have no particular effect since i r the temperature of the .dehumidifying coil. I 'It is possible that this dehumidifying action might result in the lowering of the space temperature below some permissible minimum such as 65 F. If this occurs, provision is made for opening the steam valve I16 whereby to raise the temperature of the air being delivered to the space. Even though the space temperature'is not lowered below a desirable point, the temperathe change-over relay 25 is in its summer position. Power is supplied to the relay coil .4|6 by the secondary 426 of a step-down transformer that has aprimary 421. Energization of this usual manner, crank includes e0 transformer isalso controlled by the change-Q over relay 25 and the circuit for the-primary 21 is as follows: line wire 253, switch arm 28,

and wire 429 to ground 256. Now, when the relative humidity of the space rises to or thereabove, so as to sequentially 4 into engagement with cooperating contacts 2 and H3, relay coil M6 is energized as follows: secondary 426, wire 430, contact 4I2, contact arm 4I0, contact arm 4| I, contact 4I3, wire 43I, relay coil 6 and wire 432 to the other side of secondary 426. Energizetion of relay coil 4I6 moves switch arm 3 into engagement with contact 433 (for a purpose :29, wire :30, wire 42:, wire :as the temperature control resistance 448. that the control contact left-hand end of the control resistance 448 when protective resistance 2| I, whereas the ture of the air discharged into the space may be so lowered that a cold draft results. The present invention contemplates the opening of the steam valve I16 not by the temperature of the space but by the temperature of the airbeing discharged into the space.

Referring again to Fig. 3, an indoor controller at, 440. This controlleris generally indicated comprises a bell crank that is pivoted at I and includes an arm 442'whichis positioned by a pressure device in the form of a bellows 443. This bellows 443 is connected with controlling bulb 444 by a connecting tube 445. The bellows 443, controlling bulb 444, and connecting tube 445 are charged with a suitable volatile or expansible fluid whereby the pressure in bellows creased upon temperature rise. Controlling bulb 444 is located in the discharge from the air conditioning chamber I0 so as to, respond to the temperature of the air discharged therefrom. The pressure in bellows 443 'is'opposed, in the by a coiled spring 446. This bell a further arm 441 which takes the form of "a control contact. Thearrangement is such 441' engages the extreme the 'iiischargetemperature falls to 65 F. The control contact 441 continues to falland reaches the extreme right-hand end thereof when the discharged air temperature reaches 60 F. It will be noted that the left-hand end of control resistance 448 is connected to the left-hand end of solenoid coil I93 by wire 449, wire 2|9 and right-hand end of control resistance 448 is connected to the right-hand end wire 2|3, protective resistance 2 III, wire 2I2 and and contact 3 and this the tempera- 443 is inthat cooperates with a traverses this resistance 448 l of solenoid coil I 94 by wire 450,

f and protective resistance wire 208. fore connected in parallel with theseries-connected solenoid coils I93 and I94, through the. protective resistances 2III and 2| I. The control contact 441 is connected to contact 433 by wire 45L As a result, when the change-over relay 25 is in its summer position,

cessive humidity conditions as just described above, the control contact 1 is connected to the junction of solenoid coils I93 and I9l'by wire 45I, contact 433, switch arm 3| I, wire 3I9, contact 39, switch arm 3|, wire'228 and wire 225. Therefore, whenever the relative humidity becomes excessive and energizes'the relay coil 9, the control potentiometer 8 is placed in control of motor mechanism 46-! that controls the steam valve I16. So long as the discharge air temperature remains at or above 65? F., control contact finger 1 engages the wire 9 so that the solenoid coil I93 is substantially short-ciras shown, and,when the relay coil 6 is energized by reason of ex trol of the taking in of cuited by the following circuit: from the junction of solenoid coils I93 and I94, wire 22!, wire 223, switch arm 3|, contact 39, wire 3I9, switch arm 3, contact 133, wire "I, wire 9, wire 2I9, III to the left-hand end of solenoid coil I93. The steam valve I19 therefore remains closed. However; should the discharged air temperature fall below 65 F., part of the control resistance Bis placed in this shunt circuit so that the solenoid coil I93 receives more current and the steam valve I19 must move partly open in order for balancing contact I to move upwardly along balancing resistance 229 to rebalance the energizations of the solenoid coils I93 and I94. In thismanner, as the discharge temperature falls, the steam valve is opened more and more widely audit the discharge air temperature falls to 60 F. so that control contact 1 engages wire 459, then the steam valve I16 is moved to its full open position. This opening of the steam valve reheats the air'which is being discharged from the air conditioning chamber and prevents the discharge of unduly cold air into the space so as to prevent the formation or unpleasant drafts and prevents the ultimate lowering of the space temperature below-the desired value.

Summary To summarize the operation of the system of the present invention, the change-over from sumby to prevent the condensation of moisture pletely opened under the control mer control to winter controland vice versa is' accomplished bymeans responsive both to the temperature of the space to be controlled and to the outdoor temperature so that the apparatus operates on a summer cycle if either of these temperatures is sufllciently high and can only operate on a winter cycle when both of these temperatures are below predetermined values. with the parts in the position shown in the drawings, the apparatus is operating on a summer cycle. Under these conditions, the cooling means is operated under the control of a space relative humidity responsive devic and a space dry bulb temperature responsive device in such manner as to maintain a desired or constant effective temperature. However, the effective temperature that is maintained in the space is raised as-the outdoor temperature rises, but at a slower rate, whereby a variable differential is maintained be-, tween the outdoor temperature and the indoor effective temperature. Under normal conditions of operation, no attempt is made to control the relative humidity in the summer cycle since the recondition in control of the -means for cooling air .plete closure of this The control resistance 9 is theremoval of moisture requires a larger cooling capacity than does mere cooling. However, if the relative humidity should becom excessive, then a dehumidifying action takes place. If this dehumidifying of the air passing through the air conditioning chamber results in the discharged air temperature being lowered below a desired minimum value, then a.discharged air temperature thermostat operates the winter steam valve so as to reheat the air being discharged into the space. During the summer operation, the damper in confresh air is operated from a full open position to a closed position when the outdoor temperature either rises above or falls below some optimum value such as F. However, provision is made for preventing the. comfresh air damper upon a rise in outdoor temperature it it be desired to always maintain a small amount of fresh air flow into the space. But if this small amount of fresh air flow is maintained, provision is further made to prevent this small flow of fresh air upon the outdoor temperature becoming excessive.

In the winter cycle, a control responsive to the relative humidity in the space controls the flow of water to the water spray for humidilyins purposes. This humidity responslve control has its setting or adjustment lowered as the outdoor temperature falls whereby the dew point of the air in the space is maintained below the temperature of the windows and other exposed surfaces wherethereon. A space temperature responsive dry bulb thermostat controls the application of heat to the space and the adjustment of this thermostat is raised as the outdoor temperature lowers in order to compensate for the lowering in the relative humidity maintained in the space whereby to maintain a constant effective temperature in the space at all times. During the winter operation. the. fresh air damper is normally maintained opened only a small amount but may be comof a space temperature responsive thermostat if the space tem-- perature should become excessive for any reason.

Provision is also made whereby the damper may be automatically moved under manual control to its full open position either during the winter cycle or the summer cycle for purposes of ventilation.

It will be readily appreciated that a great manychanges in the various details of the present invention, as well as in the general combination can be made without departing from the spirit thereof. We therefore intend to be limited only .by the scope of the appended claims.

We claim: I

1. In an air conditioning system for conditioning a space, in combination, means to heat and cool said space, control means in control of said heating and cooling means, electrical means associated with said control means and operative to vary the control thereof upon said heating and cooling means, a pair of switches wired in parallel in control of said electrical means, means responsive to a space condition in control of one of said switches, and means responsive to an external other of said switches. 2. A year around air conditioning system of the class described, comprising, in combination, delivered to a space to a value above its dew-point, means responsive to the eflective temperature. of the space in control of said cooling means to substantially constant,

, last-named cooling means means to cool the air delivered to the space to a value below its dew-point whereby to remove moisture therefrom, means responsive to the moisture of the air in the space in control of said and operative to cause moisture to be removed from the air being delivered to the space only in the event the moisture content of the air in the space becomes excessive, heating means for heating the air being supplied to the space, a delivered air temperature responsive thermostat in control of said heating means to prevent lowering of the delivered air temperature below a predetermined value by reason of its being cooled below its dew-point, means in control of said heating means for winter operation, and means to selectively place said last-named means in control of the heating means or to place all of said other controls in controlof the space conditioning means.

3. In an air conditioning system, in combination, means to coolair to be delivered to a space to a value above its dew-point, means responsive to the effective temperatureof the space in control of said cooling means to maintain the space eifective temperature substantially constant, means to cool the air being supplied to the space to a value below its dew-point to cause the removal of moisture therefrom, means responsive to the moisture content of the air in said space in control of said last named cooling means and operative to cause the removal of moisture from the air being supplied to the space only when the space moisture content becomes excessive, means to heat" the space, means responsive to the temperature of the space in control of said heating means, means responsive to the temperature of the air being supplied to the space for additionally controlling said heating means, and means responsive to outdoor temperature to raise the value ofthe eifective temperature maintained therein by said effective temperature responsive means as the outdoor temperature rises and to raise the value of the space temperature maintained therein by said space temperature responsive means as the outdoor temperature lowers.

4. In a control system for a space, means in control of the fio'w of fresh air to the space, means responsive to the space temperature to control said fresh air flow control means to increase the flow of fresh air to the space if the space temperature becomes higher than desired, means responsive to the outdoor temperature to control the flow of fresh air to said space, and means responsive to outdoor temperature to selectively place said space temperature or outdoor tempera ture responsive means in control of said fresh air flow control means.

5. In an air conditioning system in combination, damper means in control of the flow of fresh air to a space, means responsive to temperature conditions external to said space in control of said damper means to move the same from open posi tion to closed position upon rise or fall of said temperature above or below an optimum value, means responsive to the temperature of-said space in control of said damper means to move the same from closed position toward open position upon a rise in such temperature above a given value, and means selectively operable to place one or the other of said temperature responsive means in control of said damper means, said means including a space temperature responsive thermostat and an external temperature responsive thermostat. v

6. In an air conditioning system, in combination, damper means in control of the flow of fresh air to a space, means responsive to temperature conditions external to said space in control of said damper means to move the same from open posi tion to closed position upon rise or fall of said temperature above or below an optimum value, means responsive to the temperature of said space in control of said damper means to move the same from closed position toward open position upon a rise in such temperature above a given value. electrical means selectively operable to place one or the other of said temperature responsive means in control of said damper means, a. pair of switches in control of said electrical means,-and temperature responsive means in control of said switches.

7. In a heating and cooling system for a space, means to discharge air into said space, means to heat said air, means to cool said air, means responsive to a condition of the air in the space incontrol of said cooling means, means responsive to the temperature of the air discharged to said space to control said heating means, means responsive to the space temperature to control said heating means, and means responsive to outdoor temperature operable upon rise in outdoor temperature to place said condition responsive means in control of said cooling means and said dis charge air temperature responsive means in con trol of said heating means and upon fall in outdoor temperature to place said space temperature responsive means in control of said heating means.

8. In a control system fora space, in combina tion, means to deliver air to the space, means to heat the air delivered to the space, means to reduce the relative humidity of the space by reduc ing the temperature of the air delivered thereto to abstract moisture therefrom, a summer control in control of said air temperature reducing means operative to prevent raising of the space relative humidity above a predetermined maximum, an air discharge temperature responsive device operative to control said heating means to prevent the discharging of air below a predetermined temperaspace, means to add moisture to the space, means to cool the space, means responsive to the effective temperature of the spacein-control of said cooling means operative to maintain the effective temperature of the space substantially constant in the summer, means responsive to the space temperature in control of the heating means to maintain the temperature of the space at a predetermined value in the winter, means responsive to the relative humidity of the space in control of said moisture adding means to maintain the relative humidity at a predetermined value sponsive to the outdoor temperature for adjusting said temperature responsive means and said humidity responsive the relative humidity and raise the temperature of the space in the Winter upon lowering of the outdoor temperature and means responsive to a condition indicative of a need for heating or in' the winter, means re-,

means in a manner to lower 

